Choosing the right domain name is important, and one important choice is which type of domain name suffix (ending) you should use.

Local services
For selling products or services within Australia a .com.au domain name is generally more effective in marketing terms than a .com domain. There are a number of reasons for this, basically all boiling down to the fact that the domain name looks more local and thus more relevant to Australian consumers. To qualify for an Australian domain, a business generally needs an Australian presence of some sort.
Implications for search engines
Search engines that offer a local search may also use the domain name to determine what is local and what is not.
For example, Anzwers and
GoEureka both offer an Australia-only search, and these searches will only show Australian domain names. This means that even if you are an Australian business, and have your web site in Australia, you may be missing our on reaching your Australian visitors if you use a domain ending other than the preferred local choice of .com.au.
Marketing to the USA
The above is true for most countries of the world, the only notable major exception being the USA where the .us extension is only recently gaining in popularity. If you are selling into the UK, a .uk domain is the best choice; similarly .nz will look much more local to a New Zealand audience than trying to sell your products or services under a different country code domain.
If you are looking to market to the US, the .com domain ending is nearly always going to be the best choice.
Aiming for the world
If you aiming for a global feel to your business and want to reach customers in many different countries, a generic ending like .com is also a good choice. For a service aimed at several different countries, you could consider any of the gTLDs depending on the nature of your web site, i.e. .com, .net, .org, .biz or .info.
If you already sell to multiple countries, or have any aspirations of doing so, you should consider buying more than one domain name to accomodate this - e.g. both a .com.au and a .com domain name. It will be much cheaper to do this now rather than later. Buying domains back from the secondary market later will normally cost many times more than your original purchase cost. The more well-known or generic your brand name, the more likelihood you will run into problems securing the domains you need for later expansion.
Managing multiple domains
If you do decide to have several domains, we can make it easy to keep them all under control. You don't necessarily need to expand rapidly in the short term, or to make any drastic changes to your business. We can easily redirect your new overseas domain names to your existing web site and email address.